The present invention relates generally to apparatus and methods for treating vascular conditions, and more specifically, to a wire guide having at least one variable stiffness region, and a method for varying the stiffness of at least a portion of the wire guide.
Wire guides are commonly used in vascular procedures, such as angioplasty procedures, diagnostic and interventional procedures, percutaneous access procedures, and radiological and neurological procedures. In general, wire guides may be used to introduce a wide variety of medical devices into the vascular system.
For example, wire guides may be employed to treat atherosclerosis and other occlusive diseases, which are prevalent among a significant portion of the population. In such diseases, atherosclerotic plaque forms on the walls of the vessel and blocks or restricts blood flow through the vessel. Atherosclerosis commonly affects the coronary arteries, the aorta, the iliofemoral arteries and the carotid arteries. Several serious conditions may result from the restricted blood flow, such as ischemic events.
Various procedures are known for treating stenoses in the arterial vasculature, such as the use of balloon angioplasty and stenting. During a balloon angioplasty procedure, a catheter having a deflated balloon attached thereto is positioned across a constricting lesion, and the balloon is then inflated to widen the lumen to partially or fully restore patency to the vessel.
Stenting involves the insertion of a usually tubular member into a vessel, and may be used alone or in conjunction with an angioplasty procedure. Stents may be self-expanding or balloon expandable. Self-expanding stents typically are delivered into a vessel within a delivery sheath, which constrains the stent prior to deployment. When the delivery sheath is retracted, the stent is allowed to radially expand to its predetermined shape. If the stent is balloon expandable, the stent typically is loaded onto a balloon of a catheter, inserted into a vessel, and the balloon is inflated to radially expand the stent.
Stents also may also be used in conjunction with a stent-graft procedure, wherein the stent may be coupled to an inner or outer surface of a graft material, or disposed between layers of graft material. In stent-graft procedures, it may be desirable to place one or more stent-graft limbs in position within a main body stent-graft. In other instances, such as branch vessel stent grafting, it may be desirable to place a limb within a limb.
Generally, during each of the foregoing procedures, a wire guide is first inserted into a patient's vessel, e.g., under fluoroscopic guidance. The wire guide then is advanced toward a target site in the patient's vasculature. For example, the distal end of the wire guide may be advanced through a stenosis. Then, various medical components, such as a balloon catheter and/or stent, may be distally advanced over the wire guide to the target site.
Various wire guides comprise flexible distal regions to facilitate navigation through the tortuous anatomy of a patient's vasculature. Where such flexible distal regions are used, it may be difficult to insert a medical component over the wire guide, for example, because the flexible distal region may be susceptible to kinking. However, if the distal region of the wire guide is too rigid, then it may not be sufficiently flexible to navigate the tortuous anatomy.
Therefore, in order to facilitate advancement of medical components to the target site, some medical procedures first use a relatively flexible wire guide to navigate the patient's anatomy. Then, a buddy wire, having a slightly greater rigidity than the initial wire guide, is inserted over the initial wire guide and the initial wire guide is subsequently removed. A medical component, such as a catheter, then may be advanced distally over the buddy wire so that instances of kinking may be reduced. However, this technique requires the insertion of two wires, i.e., the initial wire guide and the buddy wire, to enable positioning of the medical components at the target site, thereby increasing the time, cost and complexity of the procedure.
In view of the foregoing, there is a need for a single wire guide having a variable stiffness suitable for navigating tortuous anatomy, but also being sufficiently rigid to permit the advancement of medical components over the wire guide.